I should know what this is

[BDofMSP]

It's never to late to learn, right?

Can someone please clue me in to the role of the big round shiny thing with the black top right in the middle of my 12 volt ships service box? (Apologies that it's sideways here) Both the port and starboard banks connect to it, so I'm curious if this is related to my starboard bank magically staying charged even though my alternator was dead on that side.

Also, what do the red and yellow wires (with the yellow terminals) coming out of it likely do?

Thanks for your patience and guidance!
BD

 

[IRENE]

A battery parallel solenoid, perhaps?? The small wires may lead to a “parallel” or “port/starboard” toggle switch, spring loaded to the off position.

 

[rochepoint]

Jeff....That would be my guess as well......

 

[Crusty Chief]

I believe Jeff hit this on the head, based on the big cable’s attached to each side.

 

[High Wire]

Look at your helm controls for an “emergency start “ or “parallel “ toggle switch. If one battery is weak then you toggle the switch to connect both battery banks together temporarily to get the other engine going. It’s intended to get you home where you can fix the problem battery.

 

[oscar]

It may be that, and more. OP states his SB bank staid charged even though the alternator was dead for a while. This makes me think it's a BIM, and possibly a SMART BIM. (Battery isolation manager). They are very common in motor homes where they sit between the house and chassis bank. So when parked the relay is open and the banks are separated. When plugged into shore power or with generator running the battery charger will be on (in the case of a motorhome on the house bank only) and the BIM senses the higher voltage and closes to allow the other bank to be charged. Same with the engine running in the other direction. Or, as stated, you can hit the switch and force it closed to connect the two banks and jump a dead side. So I suspect something along these lines.

Would be nice to get a make and model off the thing.......

 

[BDofMSP]

Ah, yes. I do have a parallel switch at the helm. Those smaller wires must run there.

I'm thinking about running a small subpanel out of there to power an oil changer. I'll try to find a part number when I'm back in there.

Thank you!
BD

 

[bayview]

Are those cables running through holes without any protection from sharp edges of the holes?

 

[ranger58sb]

Ah, yes. I do have a parallel switch at the helm. Those smaller wires must run there.

I'm thinking about running a small subpanel out of there to power an oil changer. I'll try to find a part number when I'm back in there.

Yes, you have a parallel switch. Should be a two-way rocker. I've read that one rocker direction chooses one of your main (engine-start) battery banks to activate the solenoid, and the other rocker direction chooses the other main/start bank. Might be useful to see if you can test that while you have the box open.

Surprised you don't have an Oil-X-Changr already installed as standard... I'd have guessed a 950 or 950G or something like that, plumbed for both mains, both gears, and your genset.

-Chris

 

[BDofMSP]

I was aware of the parallel switch and I've used it. I just wasn't aware of what the solenoid looked like that it was attached to. I just assumed it was magic ;-)

Oil changer was optional and they didn't choose it. Must have been very common because there's even an unused breaker for it on the panel, and both the engines are plumbed for it (but not gen or gears). The gear drain is huge - that would be a special fitting but I'm sure it exists.

 

[BDofMSP]

Are those cables running through holes without any protection from sharp edges of the holes?

Appears that way, although it's not sharp. It's been that way for 20 years and 2000 hours now, but definitely it could eventually cause a problem. I should put a grommet in there.

 

[rgano]

My twin engine Grand Banks had a starting parallel setup. There was no "Parallel" switch involved. You started one engine at a time and the two 8D batteries in banks 1 and 2 automatically paralleled for each start. Bank 3 was the generator start.